Charge forming device



Feb. 23, 1932. w, TEETER 1,846,499

CHARGE FORMING DEVICE Filed Oct. 15, 1928 4 Sheets-Sheet. 1

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Feb. 23, 1932. w; H. "I EETER CHARGE FORMING DEVICE 4 Sheets-Sheet -2 Fil ed Oct. 15. 1928 CHARGE. FORMING DEVICE Filed Oct. 15, 1928 4 Sheets-Sheet 3 N MN NN Feb. 23, 1932. i w. HJTETER 1,846,499

CHARGE FORMING DEVICE Filed Oct. 15, 1928 4 Sheets-Sheet 4 [27 man 2" 01" JJ. J r

Patented Feb. 23, 1932 PATENT FFKIE WILFOBD H. TEETER, OF DAYTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO DELCO PRODUCTS CORPORATION, OF DAYTON, CHIC, A CORPORATION OF DELAWARE CHARGE FORMING DEVICE Application filed October 15, 1928.

This invention relates to charge forming devices for internal combustion engines and more particularly to the type of charge forming device comprising a plurality of primary carburetors, one for each intake port of the engine, cooperating respectively with a plurality of secondary carburetors, each located adjacent an oli ine-intake port and receiving fuel air mixture-from a pipe connected with one of the primary carburetors, while receiving air when required through one branch of an. air manifold which supplies air to all of the secondary carburetors.

Examples of charge forming devices of this character are disclosed in the applications of Wilford H. Teeter, Serial No. 221,-

filed September 22, 1928, and Fred E. Aseltine, lVilford H. Teeter, and Carl H. Kindl, Serial No. 288,683 filed June 27, 1928.

In prior devices of this character such as those shown in the above applications, a single air valve has been employed to control the suction on the fuel jets and to control the dmission of all, or nearly all of the air entering the carburetor. Difficulty has been experienced with these devices in producing satisfactory acceleration, for the reason that with such structures the velocity of the primary mixture passing through the primary mixture passages is so low, that on opening of the throttle the increased supply of air reaches the secondary mixing chambers before the slow moving primary mixture, resulting in the formation of a lean mixture temporarily during the acceleration period.

Diiiiculty has also been experienced in supplying a mixture of proper proportions Cllli ing relatively low speed engine operation at partly open throttle. This is due to the fact that if the suction at the jets is maintained sufficient at high speeds to form a rich enough mixture. the suction will be too great at said jets during low speed operation at part throttie to form the lean mixture required during such operation to most eii'iciently operate the engine.

It is the principal object of the present invention to provide a charge forming device so constructed as to provide a charge having proper proportions of fuel and air to most Serial No. 312,509.

satisfactorily operate the engine during the acceleration period.

It is a further object of theinvention to provide a charge forming device which is provided with mixture proportioning means operable to form a mixture during high speedor other full throttle engine operation which is rich enough to most satisfactorily operate the engine under those operating conditions, but which is also effective during operation at relatively low speed, partly open throttle, to supply the lean mixture required for such operation.v 7

More specific objects ofthis invention are to provide a charge forming device of the character above referred to in which means is provided to produce a greater pressure differential between the opposite ends of the primary mixture passages under varying operating conditions whereby the velocity of flow through said tubes is increased, and a plurality of means for controlling the suction at the jets during low speed part throttle operation and low or high speed full throttle operation respectively, whereby a low suction is maintained at said jets during low speed part throttle operation to form a relatively weak mixture, while a much higher suction is maintained at the jets during full throttle operation to provide the relatively strong mixture required to give the necessary power for satisfactory fuel throttle operation.

With these objects in View, one feature of the invention consists in the provision of separate valves for controlling the admission of air to the primary mixture passages and secondary air passage, said valves being controlled by springs of different strength.

A further feature of the invention consists in the provision of a valve controlled by-pass connecting each primary mixture passage with the secondary air passage, the valve being constructed to open at high engine speeds.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to tie accompanying drawings wherein a preferred embodiment of one form of the present lnvention is clearly shown.

In the drawings:

Flg. 1 1s a plan VlGW' of the present invent1on attached to the engine cylinder head, a part of which is shown in section.

Fig. 2 1s a side elevation looking toward the engine block.

Fig. 3 1s a section on line 33 of Flg. 1.

Flg. 41s a section on line 4.-% of Fig. 1.

Fig. 5 1s a side elevation of the main carburetor unit looking from the left in Fig. 2.

Fig. 6 1s a side elevation of the main carburetor unit looklng from the right 111 Fig. 2.

Fig. 7 is a section through the secondary mlxing chamber on the line --7 of Fig. 2.

Figs. 8 and 9 are detail sections at right angles to each other of the float valve mechanism and fuel inlet passage controlled thereby.

Fig. 10 is a detail section on the line 101O of Fig. 3.

Fig. 11 is a detail view of the primary throttle valve.

The device dlsclosed herein comprises a main air manifold indicated in its en rety by the reference character 10, and having three outlet branches 11, 12 and 13, each of which is adapted to communicate with one of the ports 14 of a multi-cylindcr engine. Each port serves two adjacent cylinders through valve ports 14a and 145, as clearly indicated in Fig. 1. The cylinder head is shown in three separate fragments 15, but it will be understood that it may be an integral structure. The branches 11. 12 and 13 are each provided with an attaching flange 16, for attaching the manifold to the engine block in the conventional manner. Adjacent the inlet of the manifold is provided a flange 17 to which may be secured the main carburetor unit as shown in Fig. 3.

The main carburetor unit comprises a main housing in the form of a single casting 18. attached by screws 19 to the flange 17. An air inlet horn 20. the flow of air through which is regulated. in a manner later described, is secured in position over an opening in the upper wall of said housing by screws 22 which pass through flanges 23 and 24: on the horn and housing respectively. A. casting 25 having certain dash pot chambers and fuel passages, described in detail hereinafter, formed therein is secured by screws 26 to the lower wall of the main housing 18, a gasket being provided between the castings to make a tight joint. and a sheet metal fuel bowl 27 is held tight against a shoulder 28 on said main housing 18 by means of a screw 29 which is screwed into a post 30 depending from and integral with the casting A fuel line leading from a main source of supply communicates with the angular bore 31 in housing 18, as shown in Fig. 9. This bore connects with a vertical bore 32 in the casting 25. A nipple 38 is screwed into the lower end of bore 32 and is provided with lateral fuel outlets 3 through which fuel flows into the float chamber. The passage through the nipple is restricted at 35 to form a seat for the valve 36 which is controlled by the 3T, pivoted at SS and operated in the usual manner to maintain a constant level of fuel in the float chamber.

Fuel is conducted from the fuel bowl to a plurality of primary fuel nozzles 39, located in the primary mixing chambers in the central partof the main housing and which may, for convenience, be termed the distributor block. To conduct fuel from the fuel bowl to the nozzles, the casting 25 is provided with a vertical conduit all which communicates at its upper end with a horizontal fuel canal 42 which connects with each of the nozzles through holes 43. All of the fuel flowing through the conduit tl is admitted thereto through a metering orifice ii, at speeds up to that corresponding to a Vehicular speed of approximately 20 miles per hour. At higher speeds fuel is also admitted to the conduit 41 through an orifice 45 controlled by a fuel valve a6, oper ted in a manner fully described hereinafter, and thence through a horizontal channel l7 connecting with the lower end of channel 41.

Fuel

is lifted froin the fuel bowl to the primary mixing chambers by the suction therein. "v -Jhen the throttle is moved toward closed bOSltlOll there IS a sudden reduction in suction on the vertical column of fuel between the fuel. bowl and the nozzles which might permit the column to drop enough to cause a temporary fuel starving of the engine unless means were provided to prevent no action. F or this purpose a check valve provided in an enlarged chamber 49 at the junction of channels a1 and 42 and on reduction of suction in the primary mixing chambers seats on an annular rib 50 proiecting upwardly from the bottom of cham-- her around the upper end of the conduit 41, preventing downward flow through said conduit.

Each primary fuel nozzle is provided w'th a main fuel outlet in the top of the nozzle and a secondary fuel outlet comprising two small holes 51 and 52 diametrically opposite each other near the bottom of the vertical wall of said nozzle. At higher engine speeds there is sufficient suction in the primary mixing chambers to lift fuel through the main fuel outlet in the top of each nozzle as well from holes 51 and 52. During idling and low speed operation under load. however. the suction is only sufficient to lift the foe to a point between the orifices 51 and and the top of the nozzle. fuel flowing from said orifices by the action of gravity. Each fuel nozzle provided with a restricted fuel metering orifice The primary mixing chambers 40 connect with smaller passages 60 which may, for convenience. be termed primary mixture passages. There are three of these passages in the distributor block as indicated in Fig. i and such passages are parallel to each other and close together. These passages communicate with passages 61 formed in the wall of the manifold. The middle passage 61 is strai ht and receives a tube 62 which conveys primary mixture to the secondary mixing chamber associated with the branch 12 of the manifold. The other two passages are L-shaped and connect with pipes 63 which communicate with tubes 6d and 65, located in the manifold branches 11 and 13 and of the same construction as tube 62. This construction forms no part of the present invention and need not be more fully disclosed herein. The mixture passages 60 are restricted at the point of connection with the mixing chamhere 40 as indicated at 66, for the purpose of reducing the velocity of the air current passing the nozzles.

A single throttle valve 67 is rotatably mounted in the housing 18 and controls all of the mixture passages 60. Thisthrottle is provided with grooves 68 which register with the said passages and spindles 69 project from each end thereof outside the housing, so that certain valve operating connections, hereinafter described, may be secured thereto. A groove 7 O is provided in the throttle which cooperates with the inner end of a screw 71, adjustable in the casting, to prevent longitudinal movement of the throttle. This throttle controls the flow of primary mixture from the primary mixing chambers through the pipe connections described in the preceding paragraph to the secondary mixing chambers, where such mixture may be mixed with additional air in the manner hereinafter described.

In devices of this character previously known substantially all the air entering the device is admitted through one air inlet to a main air chamber from which air flows to both the primary and the secondary mixing chambers. According to the present invention, however, separate air inlets admit air to separate air chambers from which the air is conducted to the primary and secondary mixing chambers. The air inlet horn 20, above referred to, constitutes the main or secondary air inlet which admits air to a main or secondary air chamber formed in the upper part of the main housing, while a primary air inlet passage 81 admits air to a primary air chamber 82 formed in the main housing and separated from the secondary air chamber by a partition 83, and communicating with all of the primary mixture passages. The inlet 20 and chamber 80, although supplying air to the secondary mixing chambers, are the main inlet and main air chamber because the major portion of the air passes therethrough.

Admission of air to the primary air chamber is controlled by a valve 84, mounted on a stem 85 slidably received in a recess formed in a plug 86, screwed into the partition 88. The valve is normally held against a seat 87 by means of a spring 88 received between the upper side of the valve and a shoulder 89 formeu on the. above mentioned plug. The spring 88 is comparatively weak for a purpose to be set forth hereinafter.

Flow of air through the air horn 20 is con trolled by the main or secondary air valve 90 which is normally held against a seat 91 by a spring 92, which is stronger than spring 88 for a purpose later explained. An air conduit 105 controlled by a valve mechanism later described, connects the air chamber 80 with the air manifold to supply air thereto during certain operating conditions.

The air valve 90 is adjustably secured on a stem 93 slidably mounted in a guide sleeve 94.- iixed in the housing. A sleeve 95 is slidably mounted on the guide sleeve and at its lower end is provided with an annular projecting flange 96 which serves as a seat for the air valve spring 92. This sleeve is adapted to be lifted into engagement with the under side of the air valve, to choke the carburetor to facilitate starting, by'means of an arm 97 secured to a rock shaft 98 rotatably mounted in the wall of the main housing. The arm 97 is provided with two pins 99 and 100 engaging opposite sides of the flange 96, while the shaft 98 projects through the casing where it is bent to provide an operating arm 101 having a hole 102 in which some form of operating connection may be attached. An adjustable stop screw 103 is provided on the outside of the housing to determine the normal position of arm 97 and thus regulate the normal tension of the valve spring. To prevent opening or the valve 90 sufficiently to lean the mixture on opening of the throttle and to prevent fluttering of said valve, a dash pot is provided, comprising a piston 104 secured to the lower end of the valve stem and sliding in a cylinder 106 formed in the casting 25. The valve 90 and controlling means therefor is substantially the same as that disclosed in the prior applications above noted and its specific construction forms no part of the present invention.

During operation at all engine speeds bei low that corresponding to a vehicular speed of approximately 2025 miles per hour on a level road, the primary mixture is of properly combustible proportions and is conveyed to theengine wi hout admixture with additional air. At higher engine speeds, however, the velocity of flow through the primary mixing chambers is so great that a velocity head would be created at the nozzles and would increase to such an extent, unless means were provided to prevent it, that a super rich primary mixture would be formed. To obviate this difficulty the secondary air passage 105 leading from the air chamber 80 to the air manifold is controlled by an air throttle 107 mounted on a shaft 108 rotatably mounted in the housing. This air throttle is operated concurrently with the primary throttle by means which will now be described and in such a way that the air throttle does not start to open until the engine is operating at the speed above referred to.

The throttle operating mechanism comprises an operating arm 110 secured to one of the spindles 69 outside the housing, and provided with a hole 111 in which some suitable form of operating connection extending from a point convenient to the operator of the vehicle, is adapted to be attached. The arm 110 is connected by a lost motion connection to an arm 112 secured by a split clamp to the end of shaft 108 outside the housing. A link 113 is pivotally connected to arm 110 and a pin 11 1 projecting from the fore end of arm 112 projects through a slot 115 in said link. A regulating screw 116 is threaded in lugs 117 projecting from the link and is adjustable to regulate the length of the slot 115, the upper end of the screw projecting beyond the lower end of the slot. A tension spring 118 is connected to the pin 11% and to the upper end of the link. The spring tends to hold the pin against the upper end of slot 115. With botn throttles closed the parts are in the position shown in Fig. 6, with the pin 11 1 in engagement with the screw 116. As the arm 110 is rotated in a clockwise direction to open the throttles the link 113 moves downwardly to a position where the upper end of slot 115 strikes pin 114 before the arm 112 of the air throttle is moved, so that the primary throttle is partially opened before the air throttle begins to open. The screw 11G limits the closing movement of the primary throttle and adjustment of the screw regulates the throttle opening at idling.

Air is admitted so rapidly when the air throttle 107 is opened that it has been found necessary to admit more fuel than will be admitted through the metering orifice 1 1 to pre vent the mixture becoming too lean. For this reason, means have been provided for opening the valve 'a'G to permit flow through the orifice 15 when throttle 107 is opened. This means comprises an arm 120 pivoted at 121 on the outside of housing 18 as shown in Fig. 5. Projecting from the opposite end of said arm is a pin 122 which engages a slot 121 in the enlarged head 125 threaded on the upper end of the valve 46. A cam 126 is fixed oh the spindle 69 projecting from the end of throttle 67 opposite to that on which the operating arm 110 is secured, and cooperating with this cam is a roller 127 rotatably mounted on a pin projecting from the arm 120. A

part of the cam is concentric relative to its operating shaft, so that it is inelfective to lift arm 120 and open the valve 46 until a certain predetermined speed has been reached, for example, that corresponding to a vehicular speed of 20 25 miles per hour. By substituting cams of different shape or providing a cam which is adjustable on its shaft, the engine speed at which the fuel valve begins to open may be regulated as desired. The above described mechanism and the throttle operating mechanism are substantially the same as those disclosed in the earlier cases and are not a part of the present invention.

As in the devices disclosed in the above mentioned earlier applications, the secondary mixing chambers comprise Venturi tubes -30 or other flow accelerating elements. There are three of these tubes of identical construction, one of which is positioned in each of the branches 11, 12, and 13 of the manifold so that the point of greatest depression or suction in each tube is immediately adjacent the outlet end of the primary mixture tube associated therewith. Each venturi is provided with an external rib 131 which fits, when the manifold is attached to the engine block, both in the engine intake port and in a recess 132 in the end of the associated branch of the manifold, the rib being clamped between shoulders 133 and 134 in the manifold and intake port respectively when the device is assembled. The Venturi tubes cause the air entering the air manifold to move past the ends of the primary mixture tubes at relatively high velocity at all times when air is admitted to the secondary mixing chambers.

As previously stated, the spring 88 which holds the primary air valve closed is a relatively weak spring which is provided to accomplish two results. First, it oppose little resistance to the opening of the air valve so that even at low speeds the air valve may open a considerable amount, thus admitting suilicient primary air while maintaining a relatively low suction at the fuel jets to form a relatively lean mixture at low speeds, and correcting a tendency, noticeable in early devices of this character, and due to the higher suction at the fuel jets as determined by the stronger spring of the main air valve, to form a mixture which is too rich in the low speed range. Second, by providing a weak spring on the primary air valve, the pressure in the air chamber 82 is maintained higher than would be possible if such chamber were supplied with air from the chamber 80 and the suction therein were determined by the air valve 90. Accordingly, the pressure differential between the chamber 82 and the posterior ends of the primary mixture tubes is greater and the velocity of flow through said tubes is greater than would be possible if the Suction in chamber 82 were determinedby the secondary air valve 90. This construction, therefore, produces improved acceleration, because the time interval necessary for the rich primary mixture to reach the secondary mixing chambers on any opening movement of the throttle is reduced and more nearly approaches the time required for air to flow from the chamber 80 to the said secondary mixing chambers, whereby the increased supply of rich primary mixture and increased quantity of air resulting from the opening of the throttle reach the secondary mixing chambers nearly simultaneously. 1

However, in order to secure the advantageous results above referred to, it has been necessary to employ a spring on the primary air valve which is so weak that the'suction at the jets would be too little at higher engine speeds, or at low speed operation under heavy load with open throttle, to supply sufficient fuel to form a mixture rich enough to give the necessary power for open throttle operation. To avoid this difiiculty a plurality of ports 140 are provided in the floor of the air chamber 80, one of said ports communicating with each of the mixing chambers 40 and normally closed by a flap valve 141 pivotally mounted adjacent the floor of said mixing chamber as indicated at 142. The valves 141 are held closed by the action of gravity at all times when the suction in the chamber is less than that in the primary mixing chambers 40 and will never open until after the I air throttle 107 is opened because the suction in chamber 80 before the throttle 107 is opened is less than in the chambers 40, therefore, the suction in the primary mixing chambers under all operating conditions when the throttle 107 is closed, is determined by the spring 88 of the primary air valve. After the throttle 107 opens, however, at some predetermined throttle position the suction in chamber 80 becomes greater than that in the mixing chambers 40 and the valves 141 are opened, permitting the suction in chamber 80 to be communicated to the said mixing chambers so that the suction effective at the jets is controlled by both the primary and secondary air valves, being a mean between the suctions maintained in the air chambers 80 and 82 which is suflicient to cause a fuel flow great enough to form a primary mixture of the desired proportions.

Since the valves 141 are closed at all times when the suction in the primary mixing chambers is greater than in the air chamber 80, there can never be a flow of air from said chamber 80 to the mixing chambers.

Although a plurality of ports 140 and a plurality of valves 141 are described above, it will be obvious that a single port 140 communicating with all of the primary mixture passages and a single valve 141 controlling this one port 140 may be provided as an alternative construction.

While the form of embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A charge forming device for internal combustion engines comprising a primary mixing chamber, means for supplying fuel and air thereto, a throttle, a secondary mixing chamber, a primary mixture conduit conveying the primary mixture from said primary mixing chamber to the secondary mixing chamber, primary and secondary air chambers for supplying air to said primary and secondary mixing chambers, separate air inlets for admitting air to said primary and secondary air chambers, and separate means for controlling the admission of air to said air chambers, said means being constructed to maintain different degrees of suction in said air chambers.

2. A charge forming device for internal combustion engines comprising a primary mixing chamber, means for supplying fuel and air thereto, a throttle, a secondary mixing chamber, a primary mixture conduit conveying the primary mixture from said primary mixing chamber to the secondary mixing chamber, primary and secondary air chambers for supplying air to said primary and secondary mixing chambers, separate air inlets for admitting air to said primary and secondary air chambers, and suction operated means for controlling the admission of air to said air chambers, said means being responsive to different degrees of suction, whereby different degrees of suction are maintained in said air chambers.

3. A charge forming device for internal combustion engines comprising a primary mixing chamber, means for supplying fuel and air thereto, a throttle, a secondary mixing chamber, a primary mixture conduit con veying the primary mixture from said primary mixing chamber to the secondary mixing chamber, primary and secondary air chambers for supplying air to said primary and secondary mixing chambers, separate air inlets for admitting air to said primary and secondary air chambers, a valve controlling the admission of air to said. primary air chamber and adapted to admit air thereto at all times when the engine is running, and a valve controlling admission of air to said secondary air chamber and admitting air thereto during only a part of the engine operation.

4. A charge forming device for internal combustion engines comprising a primary mixing chamber, means for supplying fuel and air thereto, a secondary mixing chamber, a primary mixture conduit conveying the primary mixture from said primary mixing chamber to the secondary mixing chamber, a primary throttle controlling flow through said conduit, primary and secondary air chambers for supplying air to said primary and secondary mixing chambers, a valve controlling admission of air to the pri mary mixing chamber and adapted to open at all times during engine operation, and a valve controlling admission of air to the secondary mixing chamber and adapted to be opened at a predetermined engine speed.

5. A charge forming device for internal combustion engines comprising a primary mixing chamber, fuel and air inlets t ierefor, a secondary mixin chamber into which the primary mixture is delivered, a valve for controlling the admission of air to the primary mixing chamber, a relatively weak spring controlling said valve whereby a low suction is maintained at the fuel inlet and a higher suction in the secondary mixing chamber during relatively low speed engine operation, and other means tending to equalize the pressure in the primary and secondary mixing chambers on increase of engine speed whereby the suction at said fuel inlet is increased during engine operation at higher speeds.

6. A charge forming device for internal combustion engines comprising a primary mixing chamber, means for supplying fuel and air thereto, a secondary mixing chamber into which the primary mixture is delivered, primary and secondary air chambers supplying air to said primary and secondary mixing chambers respectively, a passage connecting the primary mixing chamber and secondary air chamber and means closing said passage at relatively low engine speeds.

7. A charge forming device for internal combustion engines comprising a primary mixing chamber, means for supplying fuel and air thereto, a secondary mixing chamber into which the primary mixture is delivered, primary and secondary air chambers supplying air to said primary and secondary mixing chambers respectively, a passage connecting the primary mixing chamber and secondary air chamber, a suction operated valve normally closing said passage and adapted to open after a predetermined openlng movement of the throttle.

8. A charge forming device for internal combustion engines comprising a primary mixing chamber, means for supplying fuel and air thereto, a secondary mixing chamber into which the primary mixture is delivered, primary and secondary air chambers supplying air to said primary and secondary mixing chambers respectively, primary and secondary air valves controlling admission of air to said air chambers and adapted to open seriatim, a passage connecting the primary mixing chamber and secondary air chamber, a valve normally closing said passage and adapted to open after the secondary air valve opens.

9. A charge forming device for internal combustion engines comprising a mixing chamber, means for supplying fuel thereto, primary and secondary air inlets, separate suction operated valves controlling admission of air thereto and adapted to open under different degr es of suction and means whereby the suction in said mixing chamber is determined by one of said valves under certain operating conditions, and means whereby the suction in said mixing chamber is determined by said primary valve at low speed, part throttle operation and is determined by both valves after a predetermined opening movement of the throttle, said means including a passage between the mixing chamber and secondary air inlet.

10. A charge forming device for internal combustion engines comprising a primary mixing chamber, means supplying fuel and air thereto, a secondary mixing chamber, a mixture conduit adapted to convey primary mixture from the primary chamber to said secondary chamber, separate air passages communicating with the atmosphere and supplying air to said primary and secondary mixi ng chambers respectively, a spring held valve controlling admission of air to the primary mixing chamber and adapted to open under relatively low suction and a spring held valve controlling admission of air to the secondary mixing chamber and opening only under relatively high suction, whereby a relatively great difference in the pressures maintained at opposite ends of the mixture conduit is elfected.

11. A charge forming device for multicylinder internal combustion engines comprising a plurality of secondary mixing chambers, a plurality of primary mixing chambers associated therewith and supplying primary mixture thereto, means supplying fuel to said primary mixing chambers, separate air inlets one of which supplies air to all of said primary mixing chambers and the other of which supplies air to all of said secondary mixing chambers, and separate valves controlling the admission of air through said inlets.

12. A charge forming device for multicylinder internal combustion engines comprising a plurality of seconda y mixing cham bers, a plurality of primary mixing chambers associated therewith and supplying primary n'iixture thereto, means supplying fuel to said primary mixing chambers, a single primary air chamber supplying air to all of said primary mixing chambers, a single secondary air chamber supplying air only to said secondary mixing chambers, and means connecting the secondary air chamber with each of the primary mixing chambers, whereby the suction in said air chamber is communicated to said mixing chambers under certain operating condltions.

18. A charge forming device for internai combustion engines comprising a primary mixing chamber, means for supplying fuel and air thereto, a secondary mixing chamher, a primary mixture conduit conveying the primary mixture from said primary mixing chamber to the secondary mixing chamber, a primary throttle controlling'the flow through said primary mixing conduit, primary and secondary air chambers for supplying air to said primary and secondary mixing chambers, separate air inlets admitting air to said primary and secondary air chambers respectively, and means for maintaining a greater suction in the secondary air chamber than in said primary air chamber during operation at open throttle.

In testimony whereof I hereto afiix my signature.

WILFORD H. TEETER. 

